One major goal of this proposal is to determine the molecular mechanism of temporal translational control during male germ cell development in the mouse. A second major objective is to investigate the role of the protamine 1 gene in the physical remodelling and the genetic reprogramming of the paternal genome during spermatogenesis. The mouse protamine 1 gene, Prm-1, is regulated at both the transcriptional and translational level. Although the gene is first transcribed postmeiotically in round spermatids, the mRNA is not translated until up to a week later in elongating spermatids. To identify the cis-acting regulatory elements in the Prm-1 mRNA that regulate its temporal translational control, fusions will be constructed between regions of the Prm-1 gene and a reporter gene and studied in transgenic mice. Cis-acting translational control elements that are identified will be cloned into different regions of an heterologous mRNA to determine if their position within an mRNA affects their function. To study the mechanism of translational control, genetic and biochemical approaches will be used to clone the gene(s) for translational control factor(s) that interact with the translational control elements. To determine the importance of temporal translational control as it pertains to protamine 1 function, the product of the Prm-1 gene will be expressed at different times during spermatogenesis. To determine if protamine 1 is essential for nuclear condensation and/or reprogramming of the paternal genome during spermatogenesis, the gene will be mutated in embryonic stem cells by homologous recombination and its effect studied in transgenic mice. Knowledge gained from these studies may ultimately contribute to the medically important problems of male infertility and the inheritance of genetic diseases.